Carboxy containing ethylene polymer resins may be ionically crosslinked by partially or completely neutralizing the acid groups with metal ions. These metal salts of carboxy containing ethylene polymer resins are called ionomer resins. Thus, ionomer resins are ionically crosslinked ethylene/acid copolymers having thermally labile crosslinks, i.e., at elevated temperatures the crosslinks are broken; this permits processing the heated resin as a thermoplastic. Upon cooling, the crosslinks reform to transform the fluid mass to a solidified mass exhibiting properties substantially the same as the original material. Carboxy containing ethylene polymer resins and ionomer resins cannot be used in applications where parts under load are exposed to highly elevated temperatures because the materials tend to creep. If the tendency to creep at elevated temperatures could be overcome, wider use of these resins would result.